This relates to a multi-node communication network and in particular to a method of simultaneously routing a plurality of messages in such a network.
A common problem in a multi node communication network is that of coping with more than one message at a time. In some systems such as the Ethernet System if two messages are provided to the network at the same time, both messages are cancelled and the senders of those messages are left to try again. In other systems, one of the two messages is selected for transmission either arbitrarily or in accordance with a specified procedure and the other message is ignored.
Neither of the above procedures is very satisfactory in any communication network and these procedures pose particular problems in any system where there is any significant interaction between the message sources at the different nodes in the communication network.
Of particular interest in the present invention is the case where the different message sources are individual processors that are connected together by the communication network to form a parallel processor. As the number of processors in a parallel processor has increased, the problem of coping with a plurality of messages in the communication network has become more acute, and numerous techniques have been developed to improve the message handling capability of the network that interconnects such processors. One such technique has been to provide hypercube interconnection networks such as those described in the above referenced U.S. Pat. No. 4,598,400 at Column 4, line 16 to Column 8, line 29 and Column 11, line 12 to Column 38, line 68. In such networks, the processors are disposed at the nodes of a hypercube and interconnected by physical wires in a connection pattern that simulates the edge of a hypercube. As a result, there are many more paths between any pair of nodes in the hypercube, and consequently many more ways of routing messages from one node to another.
Nevertheless, it still happens that there will be collisions between messages being routed in the network. Some collisions are unavoidable because the messages are routed from a plurality of different sources to the same destination. Such routing patterns can be encountered frequently, as for example, where data stored in one node is to be used in calculations performed at a multiplicity of other nodes. In such circumstances, it has been found possible to combine the various messages that are routed from the multiplicity of nodes to the single destination and store the switch settings required to execute such routing. Information from the destination node can then be returned to the multiplicity of source nodes by routing the data backwards through the connection network using the switch settings in reverse order. Such an arrangement is described in detail in the above referenced U.S. Pat. No. 4,984,235.
The present invention is directed to another method of providing connections between a plurality of source nodes on one hand and a common destination node.